As a heat-absorbing glass plate for an automobile, one made of soda lime silica glass which is green or blue as it contains coloring components, has been known.
A heat-absorbing glass plate is required to have a low solar transmittance, for example, a solar transmittance as defined in JIS R3106 (1998) (hereinafter sometimes referred to as Te) of at most 42% calculated as 4 mm thickness. Further, it is required to have a high visible light transmittance, for example, a visible light transmittance as defined in JIS R3106 (1998) (illuminant A, 2° visual field) (hereinafter sometimes referred to as Tv) of at least 70% calculated as 4 mm thickness.
Further, as a heat-absorbing glass plate, a glass plate having a green color tends to be preferred which presents a more natural color of a transmitted light when a passenger looks out of window through the glass plate.
Further, for a heat-absorbing glass plate, with a view to suppressing inclusion of impurities when the glass base (type of glass) to be used for production of glass is changed in a melting furnace and in view of the cost, it is required to reduce the number of the coloring components as far as possible and to reduce the unit price of the material for the coloring components.
As a heat-absorbing glass plate, for example, the following (1) and (2) have been proposed.    (1) A heat-absorbing glass plate (Patent Document 1) which is made of soda lime silica glass having a Redox of from 0.38 to 0.60,    containing from 0.005 to 0.18% of SO3 as represented by mass % based on oxides, and containing substantially no polysulfide, and    which contains, as coloring components, any one of I) to V) as represented by mass % or by mass ppm:    I) total iron as calculated as Fe2O3: 0.6 to 4%,
FeO: 0.23 to 2.4%,
CoO: 40 to 500 ppm,
Se: 5 to 70 ppm,
Cr2O3: 15 to 800 ppm,
TiO2: 0.02 to 1%.    II) total iron as calculated as Fe2O3: 0.4 to 1%,
CoO: 4 to 40 ppm,
Cr2O3: 0 to 100 ppm.    III) total iron as calculated as Fe2O3: 0.9 to 2%,
FeO: 0.34 to 1.2%,
CoO: 90 to 250 ppm,
Se: 0 to 12 ppm,
TiO2: 0 to 0.9%.    IV) total iron as calculated as Fe2O3: 0.7 to 2.2%,
FeO: 0.266 to 1.32%,
Se: 3 to 100 ppm,
CoO: 0 to 100 ppm.    V) total iron as calculated as Fe2O3: 0.9 to 2%,
FeO: 0.34 to 1.2%,
CoO: 40 to 150 ppm,
Cr2O3: 250 to 800 ppm,
TiO2: 0.1 to 1%.    (2) A heat-absorbing glass plate (Patent Document 2) which is made of soda lime silica glass containing, as coloring components, as represented by mass % or mass ppm based on oxides:
total iron as calculated as Fe2O3: 0.45 to 0.65%,
divalent iron as calculated as FeO: 0.23 to 0.28% and
CoO: 0 to 3 ppm, and
having a mass ratio of FeO/total Fe2O3 of from 0.35 to 0.55.
Some of heat-absorbing glass plates (1) satisfy Te≦42% (calculated as 4 mm thickness) and Tv≧70% (calculated as 4 mm thickness), but they are blue. Further, the glass plate (1) contains a large number of coloring components Cr2O3, CoO, etc., and accordingly there are problems of costs and inclusion of impurities when the glass base is changed.
Some of heat-absorbing glass plates (2) satisfy Te≦42% (calculated as 4 mm thickness) and Tv≧70% (calculated as 4 mm thickness), but they are blue. Further, when such a heat-absorbing glass plate contains CoO, there is a problem of inclusion of impurities when the glass base is changed, since CoO makes the glass blue even in a small amount.
As described above, with the heat-absorbing glass plates as disclosed in Patent Documents 1 and 2, it has been difficult to obtain one which presents green transmitted light and contains a small number of coloring components, while satisfying Te≦42% (calculated as 4 mm thickness) and Tv≧70% (calculated as 4 mm thickness).